In the US, there are 2.3 million patients with nonvalvular atrial fibrillation (NVAF), which is expected to increase to 12 million by 2050. The treatment of NVAF is estimated to cost $6.65 billion, including $2.93 billion (44%) for hospitalizations alone. The most significant morbidity and mortality associated with NVAF is embolic stroke, with 90% of thrombus originating from the left atrial appendage (LAA). Anticoagulation is the preferred treatment for NVAF patients, but clinical studies have demonstrated high levels of non-compliance and increased risk of bleeding or ineligibility for anticoagulation therapy, especially in the elderly population where the incidence of NVAF is highest. Currently, there are multiple clinically approved surgical and catheter-based LAA devices, but they continue to be plagued by peri-device leaks and thrombus formation because of residual volume, subsequently they have failed to eliminate the risk of stroke. To overcome these limitations, Cor Habere (Louisville, KY) and the University of Louisville are developing a LAA closure device with catheter- based delivery (StrokeShield system) that completely occludes and collapses the LAA to minimize the risk of stroke. The StrokeShield device is a collapsible occluder (nitinol reinforced membrane) that completely covers the LAA orifice with an expandable conical coil anchor that attaches to the outer wall of the LAA. The device is delivered using a catheter-based approach and expands to completely occlude the LAA orifice and collapse the LAA. The primary advantages of the StrokeShield system are a completely sealed LAA (no peri-device flow or residual space) and smooth endothelialized connection to the left atrial wall with minimal risk of cardiac bleeding and tamponade. In this SBIR phase I proposal, we will complete testing of the StrokeShield system to achieve required sample size to demonstrate feasibility. Upon successful demonstration of feasibility, we plan to submit a phase II proposal to complete engineering development and achieve a design freeze of the StrokeShield system by testing in human and canine models to demonstrate functional performance; reliability and hemocompatibility by completing Verification and Validation (V&V) testing in compliance with Good Manufacturing Practices (GMP); and safety and biocompatibility by completing a 60-day chronic study in a canine model in compliance with Good Laboratory Practices (GLP). The phase II experimental data will be used to support an Investigational Device Exemption (IDE) application to the Food and Drug Administration (FDA) for clinical trials in NVAF patients at risk for stroke.